The discovery of 1998 KY26, and the identification of its
10.7 minute spin period (Ostro et al. 1999), and the earlier
observations of 1995 HM and its 97.2 minute period (Steel et
al. 1997), showed that very fast rotation rates were
possible for small asteroids. Asteroids 1998 WB2, 1999 SF10,
and 1999 TY2 have recently been demonstrated to be very
rapidly rotating (Pravec et al. 2000) as well. The common
characteristic of these five fast-rotating objects is their
small size; all of them are less than about 200 meters in
diameter. Theoretical work (Harris 1996, and Pravec and
Harris 2000) suggests that a limiting rotation period of
about 2.2 hours separates objects of this size and smaller
from larger bodies. The physical interpretation for this
strong segregation of spin rates is that objects smaller
than a few hundred meters in diameter are all monolithic
bodies that retain the tensile strength to rotate at such
extreme rates. Objects much larger than a few hundred meters
in size simply do not rotate with periods shorter than 2.2
hours, as has been shown by Pravec et al. (2000). In this
work we present the lightcurve analysis of four more fast
rotators, 2000 AG6, 2000 DO8, and 2000 EB14, and 2000 HB24.
Their periods of 4.56, 10.44, 107.4, and 13.05 minutes,
respectively, and their small sizes (all are less than about
200 meters in diameter), make them similar to the already
known monolithic asteroids. We discuss the possibility of
correlations between the sizes and spin rates of all the
known monolithic asteroids. We will derive the approximate
values for the sizes, axial ratios, and specific rotational
energies of the known fast rotators. Finally, we will
suggest, on the basis of our kinematic analysis, an origin
for the small monolithic asteroids and ask whether or not
asteroids smaller than 200 meters can rotate more slowly
than the critical rotation limit.